In recent years, wireless power transmission device is proposed as a technology for charging a rechargeable battery of an electric vehicle. There are several types of wireless power transmission device, and in particular, a magnetic resonance method is used for the above-mentioned application.
As such a wireless power transmission device, for example, Patent Document 1 proposes a wireless power feeding system having an inverter circuit, a first LC parallel resonance portion, a second LC parallel resonance portion and a rectifier circuit, wherein, the inverter circuit inverts a direct current power into an alternating current power and transmits to a power feeding coil, the first LC parallel resonance portion is formed by a power feeding coil and a first capacitor provided in parallel with the power feeding coil, the second LC parallel resonance portion is formed by a power receiving coil and a second capacitor provided in parallel with the power receiving coil, and the rectifier circuit converts an alternating current power received from the power receiving coil into a direct current power.
Meanwhile, it is known that, in the wireless power transmission device, malfunction such as overvoltage may occur during power feeding, and a protection circuit is equipped to protect the circuit element from such malfunction. For example, Patent document 2 proposes a short circuit using a switching element for protecting a rectifier circuit from overvoltage. The short circuit disclosed in Patent document 2 monitors an output voltage of the rectifier circuit and operates the switching element to cause a short circuit when the output voltage exceeds a preset reference voltage value and thus protect circuit elements deposed in a stage following the rectifier circuit from the overvoltage. A semiconductor element is used as the switching element used in the short circuit.